"You are about to close a read-only terminal" popup does not appear if I select "Close Tab" from the menu again

[KalleOlaviNiemitalo]

Environment

Windows build number: 10.0.19042.867
Windows Terminal version (if applicable): Preview 1.7.572.0

Steps to reproduce

1. Start a new session, e.g. Command Prompt.
2. Press Ctrl+Shift+P to open the command palette, and choose "Toggle pane read-only mode". A lock icon appears in the tab header.
3. Right-click the tab header. A menu opens.
4. Select "Close Tab" from the menu. A warning pops up: "You are about to close a read-only terminal. Do you wish to continue?"
5. Click "Cancel".
6. Right-click the tab header again. A menu opens.
7. Select "Close Tab" from the menu.

Expected behavior

The same warning should pop up again.

Actual behavior

The warning does not pop up and the tab does not close.

Notes

If you try to close the pane by pressing Ctrl+Shift+W or choosing "Close pane" from the command palette, then that pops up the warning each time.

Related to #6981.

[KalleOlaviNiemitalo]

TerminalPage::_ShowCloseReadOnlyDialog is called from two functions:

• winrt::Windows::Foundation::IAsyncAction TerminalPage::_RemoveTab(winrt::TerminalApp::TabBase tab)
  

  terminal/src/cascadia/TerminalApp/TerminalPage.cpp

  Line 1292 in 89c9e6d

  ContentDialogResult warningResult = co_await _ShowCloseReadOnlyDialog();

• winrt::fire_and_forget TerminalPage::_CloseFocusedPane()
  

  terminal/src/cascadia/TerminalApp/TerminalPage.cpp

  Line 1689 in 89c9e6d

  ContentDialogResult warningResult = co_await _ShowCloseReadOnlyDialog();

TerminalPage::_RemoveTab is called from four functions:

• void TerminalPage::_RemoveTabViewItem(const MUX::Controls::TabViewItem& tabViewItem)
  

  terminal/src/cascadia/TerminalApp/TerminalPage.cpp

  Line 1280 in 89c9e6d

  _RemoveTab(tab);

• void TerminalPage::_CloseFocusedTab()
  

  terminal/src/cascadia/TerminalApp/TerminalPage.cpp

  Line 1667 in 89c9e6d

  _RemoveTab(tab);

• winrt::fire_and_forget TerminalPage::_CloseFocusedPane()
  

  terminal/src/cascadia/TerminalApp/TerminalPage.cpp

  Line 1713 in 89c9e6d

  _RemoveTab(tab);

• winrt::fire_and_forget TerminalPage::_RemoveTabs(const std::vector<winrt::TerminalApp::TabBase> tabs)
  

  terminal/src/cascadia/TerminalApp/TerminalPage.cpp

  Line 1749 in 89c9e6d

  co_await _RemoveTab(tab);

TerminalPage::_RemoveTabViewItem, TerminalPage::_CloseFocusedTab, and TerminalPage::_CloseFocusedPane discard the IAsyncAction returned by TerminalPage::_RemoveTab, instead of awaiting it. Does that cause the coroutine to be aborted so that some cleanup is skipped?

[zadjii-msft]

Huh. That's weird. Not totally sure why, but that's definitely happening. Thanks!

/cc @Don-Vito this seems like the kind of thing that interests you 😋

[KalleOlaviNiemitalo]

If discarding the IAsyncAction really causes this, then can the compiler be made to warn about such usage, perhaps by making C++/WinRT emit [[nodiscard]] somewhere?

[Don-Vito]

@zadjii-msft - please assign to me 😄
@KalleOlaviNiemitalo - thanks for the research (congrats for the profile picture!)

[Don-Vito]

So the problem is that click on the "close tab" goes directly for the tab->rootPane->Close(), rather than asking the TerminalPage to remove the tab (which is not very successful design decision IMHO). Unfortunately, Pane::Close sets isClosing to true, even if the closing is dismissed, and as a result the next invocations of Pane::Close do nothing:

void Pane::Close()
{
    // We should not set the Pane to closing state if Closing is dismissed.
    if (!_isClosing.exchange(true))
    {        
        _ClosedHandlers(nullptr, nullptr);
    }
}

[ghost]

🎉This issue was addressed in #9571, which has now been successfully released as Windows Terminal v1.7.1033.0.:tada:

Handy links:

• Release Notes
• Store Download

[ghost]

🎉This issue was addressed in #9571, which has now been successfully released as Windows Terminal Preview v1.8.1032.0.:tada:

Handy links:

• Release Notes
• Store Download